System for transmitting power to a remote PoE subsystem by forwarding PD input voltage

ABSTRACT

The present disclosure describes a system 400 for transmitting power to a remote Power over Ethernet (PoE) subsystem by forwarding Powered Device (PD) input voltage where the subsystem includes a PD and a Power Sourcing Equipment (PSE) device. Included is a master PSE device 402, a first subsystem 410, and a second subsystem 428. The first subsystem 410 includes a first PD 418 that includes a first power switching device 426 and a first PSE device 424. The first power switching device 426 forwards the input power from the first PD 418 to the first PSE 424 without disturbing the PoE handshaking between the devices. The second subsystem 428 receives the power from the first subsystem&#39;s 410 first PSE device 424. And the second subsystem 428 operates in a manner similar to the first subsystem 410.

TECHNICAL FIELD

This disclosure relates to Power over Ethernet (PoE) technology. Morespecifically, this disclosure invention relates to transmitting power toa remote Power over Ethernet powered device by forwarding Powered Deviceinput voltage.

BACKGROUND ART

Power over Ethernet (PoE) technology can be used to provide electricalpower to multiple electronic devices and/or systems by establishing aPoE power chain. In a typical PoE configuration a Power SourcingEquipment (PSE) unit is used to source power to a Powered Device (PD)unit. The PSE and the PD units typically reside in separate electronicdevices separated by some physical distance and are connected togethertypically using a RJ-45 type Ethernet cable. The PD provides regulatedpower to the connected subsystem where the subsystem is located.

The current PoE technology is described in the following patents.

U.S. Pat. No. 9,209,981, entitled: “Power over Ethernet on data pairsand spare pairs” describes a method where a Power over Ethernet PowerSourcing Equipment device is connected to a pair of data wires and apair of spare wires. When the PSE first powers up if it detects aPowered Device on the data wires it applies power to the data wires viaa transistor switch. Next, if it detects a PoE PD device on the sparewires it proceeds to apply PoE power to the spare wires via a secondtransistor switch. This is a method for a PoE device powering up a PDdevice directly via a switch. U.S. Pat. No. 9,209,981 is incorporated byreference for all purposes into this specification. In contrast however,one embodiment of the disclosed invention is a method to power a PowerSourcing Equipment device with the output of another Power SourcingEquipment device.

U.S. Pat. No. 9,203,628, entitled: “Method for apparatus fordistributing power over communication cabling”, describes in generalabout allowing Power Sourcing Equipment devices to power up PoweredDevice devices “directly” based on the presence of a first or secondoptional load. This reference does not disclose any PSE devices poweringother PSE devices. U.S. Pat. No. 9,203,628 is incorporated by referencefor all purposes into this specification. Again, in contrast however,one embodiment of the disclosed invention is a method to power a PowerSourcing Equipment device with the output of another Power SourcingEquipment device.

U.S. Pat. No. 8,873,370, entitled: “Power over Ethernet managementdevices and connections between Ethernet devices”, illustrates multipleembodiments that pass or repeat power from one Ethernet port to another.However, in all embodiments either a Power Sourcing Equipment device ispowering a Powered Device or in the embodiment where a Powered Device ispowering a Power Sourcing Equipment where there is a 48V powerconversion. And, in contrast however, one embodiment of the disclosedinvention is a method to power a Power Sourcing Equipment device withthe output of another Power Sourcing Equipment device. U.S. Pat. No.8,873,370 is incorporated by reference for all purposes into thisspecification.

One or more embodiments of the disclosed invention provide a unique anddistinct way for applying input power to a PoE Power Sourcing Equipmentdevice in a subsystem to turn on the PSE. One embodiment includes afeature that include local stepped up subsystem voltages, generated bythe Powered Device, which are not used to power up the Power overEthernet PSE. Instead, the input voltage to the subsystem's PD is usedand forwarded to the input of the PoE PSE in a protocol timed manner inorder not to interfere with PoE power up handshaking. Embodiments of thedisclosed invention have numerous advantages over the prior art thatinclude the following features: cost reduction, power heat dissipationreduction, and power efficiency improvement.

In another embodiment of the disclosed invention, a feature is that aPSE Powered Device powering a PD device is used to power a second PSEdevice. In the PoE protocol, Power Sourcing Equipment devices areintended to only power PD devices in a point to point topology and arenot intended to power directly another Power Sourcing Equipment devicein a PoE chain.

And in another embodiment of the disclosed invention, a feature is thatthe Power Sourcing Equipment output voltage of a first PSE is“forwarded” to the input of a second PSE via an intelligent switch thatturns on when the first PSE and a PD connected to the first PSE finalizetheir power up handshake.

SUMMARY OF INVENTION

The present disclosure describes an apparatus and method of anembodiment of an invention that is a system for transmitting power to aremote Power over Ethernet (PoE) subsystem by forwarding PD inputvoltage where the subsystem includes a Powered Device (PD) and a PowerSourcing Equipment device. This embodiment of the system includes amaster Power Sourcing Equipment device, a first subsystem, and a secondsubsystem. The first subsystem includes a first Powered Device thatincludes a first power switching device and a first Power SourcingEquipment device where the first subsystem couples to the master PowerSourcing Equipment device through a first Ethernet cable and receivespower to the first Powered Device and the first Power Sourcing Equipmentdevice using Power over Ethernet using the Power over Ethernethandshaking protocol. The first power switching device forwards theinput power from the first Powered Device to the first Power SourcingEquipment without disturbing the PoE handshaking between the devices Thesecond subsystem, said second subsystem includes a second Powered Devicethat includes a second power switching device and a second PowerSourcing Equipment device where the second subsystem couples to thefirst subsystem through a second Ethernet cable and receives power tothe second Powered Device and the second Power Sourcing Equipment deviceusing Power over Ethernet using the Power over Ethernet handshakingprotocol. The second power switching device forwards the input powerfrom the second Powered Device to the second Power Sourcing Equipmentwithout disturbing the PoE handshaking between the devices The secondsubsystem receives the power from the first subsystem's first PowerSourcing Equipment device.

The above embodiment of the invention may include one or more of thefollowing additional embodiments that may be combined in any and allcombinations with the above embodiment. One embodiment of the inventiondescribes where the first power switching device and/or the second powerswitching device uses an external switching device that further includesa Zener diode coupled with a FET transistor. Another embodiment of theinvention describes where the first power switching device and/or thesecond power switching device uses an internal switching device thatfurther includes a digital circuit using a MOSFET transistor. Anotherembodiment of the invention describes where the first subsystem and/orthe second subsystem further includes an intelligent switch coupled tothe power switching device. Another embodiment of the inventiondescribes where the first Power Sourcing Equipment device and/or thesecond Power Sourcing Equipment device further includes a battery.

In addition, the present disclosure describes an apparatus and method ofan embodiment of the invention that is a system for transmitting powerto a remote Power over Ethernet (PoE) subsystem by forwarding PD inputvoltage where the subsystem includes a Powered Device (PD) and a PowerSourcing Equipment device. This embodiment of the system includes amaster Power Sourcing Equipment device, a first subsystem, and a secondsubsystem. The first subsystem includes a first Powered Device thatincludes a first means for power switching and a first Power SourcingEquipment device where the first subsystem couples to the master PowerSourcing Equipment device through a first Ethernet cable and receivespower to the first Powered Device and the first Power Sourcing Equipmentdevice using Power over Ethernet using the Power over Ethernethandshaking protocol. The first means for power switching forwards theinput power from the first Powered Device to the first Power SourcingEquipment without disturbing the PoE handshaking between the devices.The second subsystem, said second subsystem includes a second PoweredDevice that includes a second means for power switching and a secondPower Sourcing Equipment device where the second subsystem couples tothe first subsystem through a second Ethernet cable and receives powerto the second Powered Device and the second Power Sourcing Equipmentdevice using Power over Ethernet using the Power over Ethernethandshaking protocol. The second means for power switching forwards theinput power from the second Powered Device to the second Power SourcingEquipment without disturbing the PoE handshaking between the devices.The second subsystem receives the power from the first subsystem's firstPower Sourcing Equipment device.

The above embodiment of the invention may include one or more of thefollowing additional embodiments that may be combined in any and allcombinations with the above embodiment. One embodiment of the inventiondescribes where the first means for power switching and/or the secondmeans for power switching uses an external switching device that furtherincludes a Zener diode coupled with a FET transistor. Another embodimentof the invention describes where the first means for power switchingand/or the second means for power switching uses an internal switchingdevice that further includes a digital circuit using a MOSFETtransistor. Another embodiment of the invention describes where thefirst subsystem and/or the second subsystem further includes a means foran intelligent switch coupled to the means for power switching. Anotherembodiment of the invention describes where the first Power SourcingEquipment device and/or the second Power Sourcing Equipment devicefurther includes a battery.

In addition, the present disclosure describes an apparatus and method ofan embodiment of the invention that is subsystem in a system fortransmitting power to a remote Power over Ethernet (PoE) subsystem byforwarding PD input voltage that includes a master Power SourcingEquipment device where the subsystem includes a Powered Device (PD) anda Power Sourcing Equipment device (PSE). This embodiment of the firstsubsystem couples to the master Power Sourcing Equipment device throughthe first Ethernet cable and receives power. The Powered Device includesa power switching device that forwards the input power from the firstPowered Device to the first Power Sourcing Equipment without disturbingthe PoE handshaking between the devices. The second subsystem in thesystem couples to the first subsystem through a second Ethernet cableand receives the power from the first subsystem's Power SourcingEquipment device using Power over Ethernet using the Power over Ethernethandshaking protocol.

The above embodiment of the invention may include one or more of thefollowing additional embodiments that may be combined in any and allcombinations with the above embodiment. One embodiment of the inventiondescribes where the power switching device uses an external switchingdevice that further includes a Zener diode coupled with a FETtransistor. Another embodiment of the invention describes where thepower switching device uses an internal switching device that furtherincludes a digital circuit using a MOSFET transistor. Another embodimentof the invention describes where the first subsystem further includes anintelligent switch coupled to the power switching device. And anotherembodiment of the invention describes where the Power Sourcing Equipmentdevice further includes a battery.

In addition, the present disclosure describes an apparatus and method ofan embodiment of the invention that is subsystem in a system fortransmitting power to a remote Power over Ethernet (PoE) subsystem byforwarding PD input voltage that includes a master Power SourcingEquipment device where the subsystem includes a Powered Device (PD) anda Power Sourcing Equipment device (PSE). This embodiment of the firstsubsystem couples to the master Power Sourcing Equipment device throughthe first Ethernet cable and receives power. The Powered Device includesa means for power switching. The second subsystem in the system couplesto the first subsystem through a second Ethernet cable and receives thepower from the first subsystem's Power Sourcing Equipment device usingPower over Ethernet using the Power over Ethernet handshaking protocol.

The above embodiment of the invention may include one or more of thefollowing additional embodiments that may be combined in any and allcombinations with the above embodiment. One embodiment of the inventiondescribes where the means for power switching uses an external switchingdevice that further includes a Zener diode coupled with a FETtransistor. Another embodiment of the invention describes where themeans for power switching uses an internal switching device that furtherincludes a digital circuit using a MOSFET transistor. Another embodimentof the invention describes where the first subsystem further includes anintelligent switch coupled to the means for power switching. And anotherembodiment of the invention describes where the Power Sourcing Equipmentdevice further includes a battery.

The present disclosure further describes an apparatus and method of anembodiment of the invention as described herein.

BRIEF DESCRIPTION OF DRAWINGS

To further aid in understanding the disclosure, the attached drawingshelp illustrate specific features and embodiments of the disclosure andthe following is a brief description of the attached drawings:

FIG. 1 illustrates the current PoE Technology using a typical PoE powerchain.

FIG. 2 illustrates a PoE power on handshake.

FIG. 3 illustrates an embodiment of a power switching device used in thedisclosed invention.

FIG. 4 discloses an embodiment of a PoE system using one embodiment ofthe power switching technology of the disclosed invention.

FIG. 5 discloses another embodiment of a PoE system with anotherembodiment of the power switching technology of the disclosed invention.

DISCLOSURE OF EMBODIMENTS

The present disclosure describes a system for transmitting power to aremote Power over Ethernet subsystem by forwarding PD input voltage. Thedisclosed embodiments are intended to describe aspects of the disclosurein sufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and changes may be madewithout departing from the scope of the disclosure. The followingdetailed description is not to be taken in a limiting sense, and thescope of the present invention is defined only by the included claims.

Furthermore, specific implementations shown and described are onlyexamples and should not be construed as the only way to implement orpartition the present disclosure into functional elements unlessspecified otherwise herein. It will be readily apparent to one ofordinary skill in the art that the various embodiments of the presentdisclosure may be practiced by numerous other partitioning solutions.

In the following description, elements, circuits, and functions may beshown in block diagram form in order not to obscure the presentdisclosure in unnecessary detail. Additionally, block definitions andpartitioning of logic between various blocks is exemplary of a specificimplementation. It will be readily apparent to one of ordinary skill inthe art that the present disclosure may be practiced by numerous otherpartitioning solutions. Those of ordinary skill in the art wouldunderstand that information and signals may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the description may be represented byvoltages, currents, electromagnetic waves, magnetic fields or particles,optical fields or particles, or any combination thereof. Some drawingsmay illustrate signals as a single signal for clarity of presentationand description. It will be understood by a person of ordinary skill inthe art that the signal may represent a bus of signals, wherein the busmay have a variety of bit widths and the present disclosure may beimplemented on any number of data signals including a single datasignal.

The various illustrative functional units include logical blocks,modules, and circuits described in connection with the embodimentsdisclosed herein so as to more particularly emphasize theirimplementation independence. The functional units may be implemented orperformed with a general purpose processor, a special purpose processor,a Digital Signal Processor (DSP), an Application Specific IntegratedCircuit (ASIC), a Field Programmable Gate Array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general purpose processor may be amicroprocessor, any conventional processor, controller, microcontroller,or state machine. A general purpose processor may be considered aspecial purpose processor while the general purpose processor isconfigured to fetch and execute instructions (e.g., software code)stored on a computer readable medium such as any type of memory,storage, and/or storage devices. A processor may also be implemented asa combination of computing devices, such as a combination of a DSP and amicroprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

In addition, the various illustrative functional units previouslydescribed above may include software or programs such as computerreadable instructions that may be described in terms of a process thatmay be depicted as a flowchart, a flow diagram, a structure diagram, ora block diagram. The process may describe operational acts as asequential process, many of these acts can be performed in anothersequence, in parallel, or substantially concurrently. Further, the orderof the acts may be rearranged. In addition, the software may compriseone or more objects, agents, threads, lines of code, subroutines,separate software applications, two or more lines of code or othersuitable software structures operating in one or more softwareapplications or on one or more processors. The software may bedistributed over several different code segments, among differentprograms, and across several memory devices. Similarly, operational datamay be identified and illustrated herein within modules, and may beembodied in any suitable form and organized within any suitable type ofdata structure. The operational data may be collected as a single dataset, or may be distributed over different locations including overdifferent storage devices.

Elements described herein may include multiple instances of the sameelement. These elements may be generically indicated by a numericaldesignator (e.g. 110) and specifically indicated by the numericalindicator followed by an alphabetic designator (e.g., 110A) or a numericindicator preceded by a “dash” (e.g., 110-1). For ease of following thedescription, for the most part element number indicators begin with thenumber of the drawing on which the elements are introduced or most fullydiscussed. For example, where feasible elements in FIG. 3 are designatedwith a format of 3xx, where 3 indicates FIG. 3 and xx designates theunique element.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not limit thequantity or order of those elements, unless such limitation isexplicitly stated. Rather, these designations may be used herein as aconvenient method of distinguishing between two or more elements orinstances of an element. Thus, a reference to first and second elementdoes not mean that only two elements may be employed or that the firstelement must precede the second element in some manner. In addition,unless stated otherwise, a set of elements may comprise one or moreelements.

Reference throughout this specification to “one embodiment”, “anembodiment” or similar language means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention. Thus,appearances of the phrases “one embodiment”, “an embodiment” and similarlanguage throughout this specification may, but do not necessarily, allrefer to the same embodiment.

FIG. 1 illustrates a system 100 that uses a typical Power over EthernetTechnology. The system 100 includes a Master source 102 that includes aMaster Power Sourcing Equipment (PSE) 104. The Master PSE provides Powerover Ethernet (PoE) 106 to other downstream devices typically overtwisted pair wires of a standard RJ-45 cable typically used inconnecting devices with Ethernet in a local area network system asillustrated in system 100. There are currently several types ofstandards for PoE such as IEEE 802.3 Alternate A and Alternate B. Thesestandards operate in one of two fashions, either the power is routedonto unused wires in the RJ 45 cable, or the power is routed onto wiresused for the data connections. Earlier versions of the PoE 802.3standard provided up to 15.4 W of DC power (minimum 44V DC and 350 mA)on each port with only 12.95 W of power assured to be available to thedevice. An updated version of the PoE 802.3 standard provides up to 25.5W of power. And as of the date of this disclosure, there is discussionof yet another updated PoE 802.3 standard with the ability to provideeven more power to downstream devices. The disclosed invention willoperate on any current or future versions of the PoE standards orsimilar type standards.

Returning back to FIG. 1, included in the PoE system 100 is a firstsubsystem 108 that could be another device such as a hard drive,graphics device, or any other device that connects to the network overEthernet and may use PoE using a cable such as an RJ-45 cable. The firstsubsystem 108 may include a Powered Device (PD) 110 such as previouslydescribed. The PD 110 may provide power to other components in thesubsystem via subsystem voltages 112. The PD 110 additionally mayprovide power to a switcher regulator 114 that may be used to power anincluded Power Sourcing Equipment (PSE) 116 device that is part of thefirst subsystem 108.

The typical PoE system 100 may further include a second subsystem 120that could be another device such as a hard drive, graphics device, orany other device that connects to the network over Ethernet and may usePoE using a cable such as an RJ 45 cable. The second subsystem 120receives power from the PSE 116 from the first subsystem 108. The secondsubsystem 120 may include a Powered Device (PD) 122 such as previouslydescribed. The PD 120 may provide power to other components in thesubsystem via subsystem voltages 124. The PD 120 additionally mayprovide power to a switcher regulator 126 that may be used to power anincluded Power Sourcing Equipment (PSE) 128 device that is part of thefirst subsystem 108. The PSE 128 may provide PoE 130 to other downstreamsubsystems that may need or require Power over Ethernet.

FIG. 2 illustrates a Power over Ethernet (PoE) power on handshake 200.In a PoE subsystem, a switcher regulator or similar is required to stepup the subsystem voltage to a level between 44 to 57 VDC in order topower up the subsystem Power Sourcing Equipment (PSE) device that isused to power up the next Powered Device (PD) in the PoE chain. In orderto power a subsystem PSE device with the PD input voltage, it isnecessary to create a switching mechanism that does not interfere withthe PoE power up handshaking protocol which is implemented via the PoEDC voltage lines. When a PD and PSE are first connected, there is a timeperiod where the PD communicates with the PSE via the voltage linesfollowing a turn on protocol. The PSE gradually increases its outputpower until it fully turns on at the 44-57 V range. The Detection Period202 is typically less than 500 ms. The Classification Period 204 istypically between 50 to 75 ms. The Startup Period 206 is typicallygreater than 15 microseconds. The Operation Period 208 will last as longas the device is in operation and is where the input line voltage cominginto the PD is between 44 to 57 V for the currently PoE standards. Thisinput line voltage may go higher with new and/or different standards.Finally, there is the Disconnection Period 210, when the PD is no longerusing the PoE and is the time when the output voltage of the subsystem'sPSE device goes to 0 V.

There are many issues associated with using a switcher regulator thatare typically found in all PoE subsystems, which include the following:the generation of heat in the subsystem card, switching regulator cost,and some loss in power efficiency. Embodiments of the disclosedinvention offer a different approach to powering up the downstreamsubsystem PSE devices by using a transistor switch topology thatreplaces the switching regulator. This technique has several advantagesthat include and eliminating the buildup of heat as well as improving oncost and power efficiency. Typically, the power losses across aswitching regulator can be on the low end of 5 to 10% of the transmittedpower, and in some PoE systems in can be higher. Using a power switchingtechnology as disclosed in this invention, the power losses are muchless. In addition, the overall loss in a PoE system where all of thesubsystems utilize switching regulators, the loss attributed to theregulator can be much higher as its multiplied by the number ofsubsystems in the overall system. Finally, using transistor technologyas disclosed in this invention cost much less than building a switchingregulator.

FIG. 3 illustrates one embodiment of the Power over Ethernet (PoE) powerswitching device 300. In this embodiment of the disclosed invention, atransistor switch with level detection is used to detect when therequired 44 to 57 VDC input voltage 310 has been detected. The powerswitching device in this embodiment is a combination of a FET transistor302, a 30V Zener diode 304, and two resistors 306 and 308 that connectbetween the input voltage 310 and ground 312. The components are chosenso that when the threshold voltage has been reached, the power switchingdevice will be biased open. The cathode side of Zener diode 304 isconnected to the PoE 44-57 V at the input of the Powered Device (PD).The source of FET 302 is connected to the Power Sourcing Equipment (PSE)device (not shown) ground at the input of the PD (not shown). The drainof FET 302 is connected to the ground of the subsystem PSE. The PoEvoltage lines between the master PSE and the PD in the subsystem willreach 44 to 57 VDC after the turn on handshaking protocol between thesetwo devices is completed. At this point, FET 302 will turn on andconnect the ground pin of the subsystem's PSE device to the PSE groundof the PD.

FIG. 4 discloses one embodiment of a PoE system that uses the aboveembodiment of the power switching technology. The system 400 includes aMaster source 402 that may include one or more processors, withassociated memory and/or storage (not shown separately) to perform oneor more functions associated with its purpose and/or the PoE technology.The Master source 402 may include a Master Power Sourcing Equipment(PSE) device 404 component that may also include one or more processors,with associated memory and/or storage (not shown separately) to performits power functions. The Master PSE 404 provides Power over Ethernet(PoE) with power 406 and ground 408 to other downstream devicestypically over the twisted pair wires of a standard RJ-45 cabletypically used in connecting devices with Ethernet in a local areanetwork system as illustrated in system 400.

Returning back to FIG. 4, included in the PoE system 400 is a firstsubsystem 410 that could be another device such as a hard drive,graphics device, or any other device that connects to the network overEthernet and may use PoE using a cable such as an RJ 45 cable. The firstsubsystem 410 may include one or more processors, with associated memoryand/or storage (not shown separately) to perform one or more functionsassociated with its purpose. The first subsystem 410 may include aPowered Device (PD) 418 such as previously described. In addition, thePD 418 may include one or more processors, with associated memory and/orstorage (not shown separately) to perform one or more functionsassociated with its purpose. The PD 418 receives power 420 and ground422 through connector 412 that connects subsystem 410 to the Mastersource 402. The PD 418 may provide power to other components in thesubsystem via subsystem voltages 416. The PD 418 additionally mayprovide power to a Power Sourcing Equipment device (PSE) 424 that ispart of the first subsystem 410. The PSE 424 may include one or moreprocessors, with associated memory and/or storage (not shown separately)to perform one or more functions associated with its purpose.

This embodiment of the disclosed invention uses the power switchingdevice 300 as illustrated in FIG. 3. In FIG. 4, the power switchingdevice 426 is external to PD 418 and PSE 424. The input of the powerswitching device 426 is connected internally to the PoE 44-57 V inputvoltage 420 at the input of the PD 418. The source of the FET for thepower switching device 426 is connected to PSE device 424 ground at theinput of the PD 418. The drain of the FET in the power switching device426 is connected to the ground of the subsystem PSE device 424. The PoEvoltage lines between the master PSE 404 and the PD 418 in the firstsubsystem 410 will reach 44 to 57 VDC after the turn on handshakingprotocol between these two devices is completed. At this point, the FETin the power switching device 426 will turn on and connect the PSEground pin of the first subsystem's PSE 424 to the PSE ground of the PD418. The power switching device 426 allows the PSE 424 to be turned onwithout the need of having to step up the subsystem voltages such aswhen using a switching regulator in a typical PoE system. The powerswitching device 426 reuses or “forwards” the 44 to 57 VDC input voltage420 at the first subsystem's PD 418 to the subsystem's PSE device 424without disturbing the PoE handshaking protocol between the PSE's andthe PD's.

The first subsystem 410 provides Power over Ethernet (PoE) with power450 and ground 452 to other downstream devices such as a secondsubsystem 428. When PSE device 424 in subsystem 410 turns on, the PoEpower will be available from subsystem 410 to turn subsystem 428 on. PSEdevice 424 in subsystem 410 will turn on the PD 436 in subsystem 428 byfollowing the PoE handshaking protocol. The second subsystem 428 couldbe another device such as a hard drive, graphics device, or any otherdevice that connects to the network over Ethernet and may use PoE usinga cable such as an RJ 45 cable. The second subsystem 428 may include oneor more processors, with associated memory and/or storage (not shownseparately) to perform one or more functions associated with itspurpose. The second subsystem 428 may include a Powered Device (PD) 436such as previously described. In addition, the PD 436 may include one ormore processors, with associated memory and/or storage (not shownseparately) to perform one or more functions associated with itspurpose. The PD 436 receives power 438 and ground 440 through connector430 that connects the second subsystem 428 to the first subsystem 410.The PD 436 may provide power to other components in the subsystem viasubsystem voltages 434. The PD 436 additionally may provide power to aPSE device 442 that is part of the second subsystem 428. The PSE device442 may include one or more processors, with associated memory and/orstorage (not shown separately) to perform one or more functionsassociated with its purpose. The power switching device 444 operates ina manner similar to the power switching device 426 as previouslydescribed. Finally, the second subsystem 428 may provide a PoEconnection to another subsystem through connector 432 that transmitspower 438 and ground 430 to the downstream subsystem. As previouslydescribed, PSE device 442 in subsystem 428 turns on, the PoE power willbe available from subsystem 428 to turn a downstream subsystem on. PSEdevice 442 in subsystem 428 will turn on the downstream PD in thedownstream subsystem by following the PoE handshaking protocol.

Another embodiment of the disclosed invention includes using anintelligent power switching device to control the transistor switch. Inthis embodiment, power switching device 426 and power switching device444 would include one or more processors, with associated memory and/orstorage (not shown separately) to perform one or more functionsassociated with its purpose. This embodiment provides that theappropriate subsystem 410 and subsystem 428 could control and monitorthe power directly and even allow the power to be monitored andcontrolled by other devices throughout the network. An advantage tousing an intelligent power switching device is that this allows one ormore devices in the network to report whether subsequent devices addedto the PoE chain will have sufficient power through the PoE connectionto support them.

A further advantage to an intelligent power switching device is that itwould allow upstream PoE devices to turn off, power down, or cycle downsome functionality in order to reduce power consumption to allow foradditional downstream devices to connect to the PoE chain. If there isnot sufficient power for the downstream devices, then the upstreamdevices (or other devices on the network) can be notified that there isnot sufficient power for additional devices in this PoE chain.

Another embodiment of the disclosed invention provides that a localpower source such as a battery can be attached to or included with PSEdevices 424 and/or 442. A local power source attached to a PSE can beused to allow downstream devices to connect to the system. In addition,a mid-span PoE power supply can be added in to the PoE chain so that itcan be extended with additional downstream devices.

FIG. 5 discloses another embodiment of a PoE system that uses adifferent embodiment for the power switching technology. The system 500includes a Master source 502 that may include one or more processors,with associated memory and/or storage (not shown separately) to performone or more functions associated with its purpose and/or the PoEtechnology. The Master source 502 may include a Master Power SourcingEquipment (PSE) device 504 component that may also include one or moreprocessors, with associated memory and/or storage (not shown separately)to perform its power functions. The Master PSE 504 provides Power overEthernet (PoE) with power 506 and ground 508 to other downstream devicestypically over the twisted pair wires of a standard RJ-45 cabletypically used in connecting devices with Ethernet in a local areanetwork system as illustrated in system 500.

Returning back to FIG. 5, included in the PoE system 500 is a firstsubsystem 510 that could be another device such as a hard drive,graphics device, or any other device that connects to the network overEthernet and may use PoE using a cable such as an RJ 45 cable. The firstsubsystem 510 may include one or more processors, with associated memoryand/or storage (not shown separately) to perform one or more functionsassociated with its purpose. The first subsystem 510 may include aPowered Device (PD) 518 such as previously described. In addition, thePD 518 may include one or more processors, with associated memory and/orstorage (not shown separately) to perform one or more functionsassociated with its purpose. The PD 518 receives power 520 and ground522 through connector 512 that connects subsystem 510 to the Mastersource 502. The PD 518 may provide power to other components in thesubsystem via subsystem voltages 516. The PD 518 additionally mayprovide power to a Power Sourcing Equipment device (PSE) 524 that ispart of the first subsystem 510. The PSE 524 may include one or moreprocessors, with associated memory and/or storage (not shown separately)to perform one or more functions associated with its purpose. Connectedto PD 518 and PSE 524 is ground 550.

The first subsystem 510 provides PoE with power 560 and ground 562 toother downstream devices such as subsystem 528. When PSE 524 insubsystem 510 turns on, the PoE power will be available from subsystem510 to turn subsystem 528 on. PSE 524 in subsystem 510 will turn on thePD 536 in subsystem 528 by following the PoE handshaking protocol. Thesecond subsystem 528 could be another device such as a hard drive,graphics device, or any other device that connects to the network overEthernet and may use PoE using a cable such as an RJ 45 cable. Thesecond subsystem 528 may include one or more processors, with associatedmemory and/or storage (not shown separately) to perform one or morefunctions associated with its purpose. The second subsystem 528 mayinclude a Powered Device (PD) 536 such as previously described. Inaddition, the PD 536 may include one or more processors, with associatedmemory and/or storage (not shown separately) to perform one or morefunctions associated with its purpose. The PD 536 receives power 538 andground 540 through connector 530 that connects second subsystem 528 tothe first subsystem 510. The PD 536 may provide power to othercomponents in the subsystem via subsystem voltages 534. The PD 536additionally may provide power to a Power Sourcing Equipment device(PSE) 542 that is part of the second subsystem 528. The PSE 542 mayinclude one or more processors, with associated memory and/or storage(not shown separately) to perform one or more functions associated withits purpose. Finally, the second subsystem 528 may provide a PoEconnection to another subsystem through connector 532 that transmitspower 538 and ground 540 to the downstream subsystem. As previouslydescribed, PSE 542 in subsystem 528 turns on, the PoE power will beavailable from subsystem 528 to turn a downstream subsystem on. PSE 542in subsystem 528 will turn on the downstream PD in the downstreamsubsystem by following the PoE handshaking protocol. Connected to PD 536and PSE 542 is ground 550.

In contrast to the embodiment illustrated in FIG. 4 that uses anexternal power switching device, this embodiment of the disclosedinvention use a built-in digital circuit of the PD to provide thepowered switching device. For example, PD 518 and/or 536 may contain adigital circuit that has one or more MOSFET's suitable for switchingpower in a PoE system. When the input voltage 520 rises above theon-voltage threshold for the PoE technology (such as 44-57 VDC), PD 518connects the input PSE device 524 to ground pin via power switchingdevice 526, and likewise PD 536 connects the input PSE device 542 toground pin via power switching device 544.

The PoE voltage lines between the master PSE device 504 and the PD 518in the first subsystem 510 will reach 44 to 57 VDC after the turn onhandshaking protocol between these two devices is completed. The powerswitching device 526 allows the PSE device 524 to be turned on withoutthe need of having to step up the subsystem voltages such as when usinga switching regulator in a typical PoE system. The power switchingdevice 526 reuses or “forwards” the 44 to 57 VDC input voltage 520 atthe first subsystem's PD 518 to the subsystem's PSE 524 withoutdisturbing the PoE handshaking protocol between the PSE's and the PD's.The power switching device 544 operates in a manner similar to the powerswitching device 526 as previously described.

Another embodiment of the disclosed invention includes using anintelligent power switching device to control the transistor switch. Inthis embodiment, power switching device 526 and power switching device542 would be controlled by a processor in PD 518 and a processor in PDF536 respectively. The use of an intelligent power switching device inthis embodiment provides the same features and benefits as previouslydescribe.

Another embodiment of the disclosed invention provides that a localpower source such as a battery can be attached or included with PSEdevices 524 and/or 542 with all of the same features and benefits aspreviously described. As before, a mid-span PoE power supply can beadded in to the PoE chain so that it can be extended with additionaldownstream devices.

While the present disclosure has been described herein with respect tocertain illustrated and described embodiments, those of ordinary skillin the art will recognize and appreciate that the present invention isnot so limited. Rather, many additions, deletions, and modifications tothe illustrated and described embodiments may be made without departingfrom the scope of the invention as hereinafter claimed along with theirlegal equivalents. In addition, features from one embodiment may becombined with features of another embodiment while still beingencompassed within the scope of the invention as contemplated by theinventor. The disclosure of the present invention is exemplary only,with the true scope of the present invention being determined by theincluded claims.

We claim the following invention:
 1. A system for transmitting power toa remote Power over Ethernet (PoE) subsystem by forwarding PoweredDevice (PD) input voltage where the subsystem includes a Powered Deviceand a Power Sourcing Equipment device (PSE), comprising: a master PowerSourcing Equipment device; a first subsystem, said first subsystemfurther comprises a first Powered Device that includes a first powerswitching device and a first Power Sourcing Equipment device, said firstsubsystem couples to said master Power Sourcing Equipment device througha first Ethernet cable and receives power to said first Powered Deviceand said first Power Sourcing Equipment device using Power over Ethernetusing the Power over Ethernet handshaking protocol, said first powerswitching device uses an external switching device that further includesa Zener diode coupled with a FET transistor, said first power switchingallows said first Power Sourcing Equipment to be turned on without theneed of stepping subsystem voltages, said first power switching deviceforwards the input power from said first Powered Device to said firstPower Sourcing Equipment without disturbing the PoE handshaking betweenthe devices; and a second subsystem, said second subsystem furthercomprises a second Powered Device that includes a second power switchingdevice and a second Power Sourcing Equipment device, said secondsubsystem couples to said first subsystem through a second Ethernetcable and receives power to said second Powered Device and said secondPower Sourcing Equipment device using Power over Ethernet using thePower over Ethernet handshaking protocol, said second power switchingdevice uses an external switching device that further includes a Zenerdiode coupled with a FET transistor, said second power switching allowssaid second Power Sourcing Equipment to be turned on without the need ofstepping subsystem voltages, said second power switching device forwardsthe input power from said second Powered Device to said second PowerSourcing Equipment without disturbing the PoE handshaking between thedevices; wherein the output of said first subsystem's first PowerSourcing Equipment device provides power to the input of said secondsubsystem's second Power Sourcing Equipment device.
 2. The system ofclaim 1 wherein said first subsystem and/or said second subsystemfurther comprises an intelligent switch coupled to the power switchingdevice.
 3. The system of claim 1 wherein said first Power SourcingEquipment device and/or said second Power Sourcing Equipment devicefurther comprises a battery.
 4. A system for transmitting power to aremote Power over Ethernet (PoE) subsystem by forwarding Powered Device(PD) input voltage where the subsystem includes a Powered Device and aPower Sourcing Equipment device (PSE), comprising: a master PowerSourcing Equipment device; a first subsystem, said first subsystemfurther comprises a first Powered Device that includes a first powerswitching device and a first Power Sourcing Equipment device, said firstsubsystem couples to said master Power Sourcing Equipment device througha first Ethernet cable and receives power to said first Powered Deviceand said first Power Sourcing Equipment device using Power over Ethernetusing the Power over Ethernet handshaking protocol, said first powerswitching device uses an internal switching device that further includesa digital circuit using a MOSFET transistor, said first power switchingallows said first Power Sourcing Equipment to be turned on without theneed of stepping subsystem voltages, said first power switching deviceforwards the input power from said first Powered Device to said firstPower Sourcing Equipment without disturbing the PoE handshaking betweenthe devices; and a second subsystem, said second subsystem furthercomprises a second Powered Device that includes a second power switchingdevice and a second Power Sourcing Equipment device, said secondsubsystem couples to said first subsystem through a second Ethernetcable and receives power to said second Powered Device and said secondPower Sourcing Equipment device using Power over Ethernet using thePower over Ethernet handshaking protocol, said second power switchingdevice uses an internal switching device that further includes a digitalcircuit using a MOSFET transistor, said second power switching allowssaid second Power Sourcing Equipment to be turned on without the need ofstepping subsystem voltages, said second power switching device forwardsthe input power from said second Powered Device to said second PowerSourcing Equipment without disturbing the PoE handshaking between thedevices; wherein the output of said first subsystem's first PowerSourcing Equipment device provides power to the input of said secondsubsystem's second Power Sourcing Equipment device.
 5. The system ofclaim 4 wherein said first subsystem and/or said second subsystemfurther comprises an intelligent switch coupled to the power switchingdevice.
 6. The system of claim 4 wherein said first Power SourcingEquipment device and/or said second Power Sourcing Equipment devicefurther comprises a battery.
 7. A method for manufacturing a system fortransmitting power to a remote Power over Ethernet (PoE) subsystem byforwarding Powered Device (PD) input voltage where the subsystemincludes a Powered Device and a Power Sourcing Equipment device (PSE),comprising: providing a master Power Sourcing Equipment device; couplinga first subsystem to said master Power Sourcing Equipment device, saidfirst subsystem further comprises a first Powered Device that includes afirst power switching device and a first Power Sourcing Equipmentdevice, said first subsystem couples to said master Power SourcingEquipment device through a first Ethernet cable and receives power tosaid first Powered Device and said first Power Sourcing Equipment deviceusing Power over Ethernet using the Power over Ethernet handshakingprotocol, said first power switching device uses an external switchingdevice that further includes a Zener diode coupled with a FETtransistor, said first power switching allows said first Power SourcingEquipment to be turned on without the need of stepping subsystemvoltages, said first power switching device forwards the input powerfrom said first Powered Device to said first Power Sourcing Equipmentwithout disturbing the PoE handshaking between the devices; and couplinga second subsystem to said first subsystem, said second subsystemfurther comprises a second Powered Device that includes a second powerswitching device and a second Power Sourcing Equipment device, saidsecond subsystem couples to said first subsystem through a secondEthernet cable and receives power to said second Powered Device and saidsecond Power Sourcing Equipment device using Power over Ethernet usingthe Power over Ethernet handshaking protocol, said second powerswitching device uses an external switching device that further includesa Zener diode coupled with a FET transistor, said second power switchingallows said second Power Sourcing Equipment to be turned on without theneed of stepping subsystem voltages, said second power switching deviceforwards the input power from said second Powered Device to said secondPower Sourcing Equipment without disturbing the PoE handshaking betweenthe devices; wherein from the output of said first subsystem's firstPower Sourcing Equipment device provides power to the input of saidsecond subsystem's second Power Sourcing Equipment device.
 8. The methodof claim 7 wherein said first subsystem and/or said second subsystemfurther comprises an intelligent switch coupled to the power switchingdevice.
 9. The method of claim 7 wherein said first Power SourcingEquipment device and/or said second Power Sourcing Equipment devicefurther comprises a battery.
 10. A method for manufacturing a system fortransmitting power to a remote Power over Ethernet (PoE) subsystem byforwarding Powered Device (PD) input voltage where the subsystemincludes a Powered Device and a Power Sourcing Equipment device (PSE),comprising: providing a master Power Sourcing Equipment device; couplinga first subsystem to said master Power Sourcing Equipment device, saidfirst subsystem further comprises a first Powered Device that includes afirst power switching device and a first Power Sourcing Equipmentdevice, said first subsystem couples to said master Power SourcingEquipment device through a first Ethernet cable and receives power tosaid first Powered Device and said first Power Sourcing Equipment deviceusing Power over Ethernet using the Power over Ethernet handshakingprotocol, said first power switching device uses an internal switchingdevice that further includes a digital circuit using a MOSFETtransistor, said first power switching allows said first Power SourcingEquipment to be turned on without the need of stepping subsystemvoltages, said first power switching device forwards the input powerfrom said first Powered Device to said first Power Sourcing Equipmentwithout disturbing the PoE handshaking between the devices; and couplinga second subsystem to said first subsystem, said second subsystemfurther comprises a second Powered Device that includes a second powerswitching device and a second Power Sourcing Equipment device, saidsecond subsystem couples to said first subsystem through a secondEthernet cable and receives power to said second Powered Device and saidsecond Power Sourcing Equipment device using Power over Ethernet usingthe Power over Ethernet handshaking protocol, said second powerswitching device uses a transistor switch topology, said second powerswitching allows said second Power Sourcing Equipment to be turned onwithout the need of stepping subsystem voltages, said second powerswitching device forwards the input power from said second PoweredDevice to said second Power Sourcing Equipment without disturbing thePoE handshaking between the devices; wherein from the output of saidfirst subsystem's first Power Sourcing Equipment device provides powerto the input of said second subsystem's second Power Sourcing Equipmentdevice.
 11. The system of claim 10 wherein said first subsystem and/orsaid second subsystem further comprises an intelligent switch coupled tothe power switching device.
 12. The system of claim 10 wherein saidfirst Power Sourcing Equipment device and/or said second Power SourcingEquipment device further comprises a battery.
 13. A method for using asystem for transmitting power to a remote Power over Ethernet (PoE)subsystem by forwarding Powered Device (PD) input voltage where thesubsystem includes a Powered Device and a Power Sourcing Equipmentdevice (PSE), comprising: providing a master Power Sourcing Equipmentdevice; receiving power to a first subsystem, said first subsystemfurther comprises a first Powered Device that includes a first powerswitching device and a first Power Sourcing Equipment device, said firstsubsystem couples to said master Power Sourcing Equipment device througha first Ethernet cable and receives power to said first Powered Deviceand said first Power Sourcing Equipment device using Power over Ethernetusing the Power over Ethernet handshaking protocol, said first powerswitching device uses an external switching device that further includesa Zener diode coupled with a FET transistor, said first power switchingallows said first Power Sourcing Equipment to be turned on without theneed of stepping subsystem voltages, said first power switching deviceforwards the input power from said first Powered Device to said firstPower Sourcing Equipment without disturbing the PoE handshaking betweenthe devices; and receiving power to a second subsystem, said secondsubsystem further comprises a second Powered Device that includes asecond power switching device and a second Power Sourcing Equipmentdevice, said second subsystem couples to said first subsystem through asecond Ethernet cable and receives power to said second Powered Deviceand said second Power Sourcing Equipment device using Power overEthernet using the Power over Ethernet handshaking protocol, said secondpower switching device uses an external switching device that furtherincludes a Zener diode coupled with a FET transistor, said second powerswitching allows said second Power Sourcing Equipment to be turned onwithout the need of stepping subsystem voltages, said second powerswitching device forwards the input power from said second PoweredDevice to said second Power Sourcing Equipment without disturbing thePoE handshaking between the devices; wherein from the output of saidfirst subsystem's first Power Sourcing Equipment device provides powerto the input of said second subsystem's second Power Sourcing Equipmentdevice.
 14. The method of claim 13 wherein said first subsystem and/orsaid second subsystem further comprises an intelligent switch coupled tothe power switching device.
 15. The method of claim 13 wherein saidfirst Power Sourcing Equipment device and/or said second Power SourcingEquipment device further comprises a battery.
 16. A method for using asystem for transmitting power to a remote Power over Ethernet (PoE)subsystem by forwarding Powered Device (PD) input voltage where thesubsystem includes a Powered Device and a Power Sourcing Equipmentdevice (PSE), comprising: providing a master Power Sourcing Equipmentdevice; receiving power to a first subsystem, said first subsystemfurther comprises a first Powered Device that includes a first powerswitching device and a first Power Sourcing Equipment device, said firstsubsystem couples to said master Power Sourcing Equipment device througha first Ethernet cable and receives power to said first Powered Deviceand said first Power Sourcing Equipment device using Power over Ethernetusing the Power over Ethernet handshaking protocol, said first powerswitching device uses an internal switching device that further includesa digital circuit using a MOSFET transistor, said first power switchingallows said first Power Sourcing Equipment to be turned on without theneed of stepping subsystem voltages, said first power switching deviceforwards the input power from said first Powered Device to said firstPower Sourcing Equipment without disturbing the PoE handshaking betweenthe devices; and receiving power to a second subsystem, said secondsubsystem further comprises a second Powered Device that includes asecond power switching device and a second Power Sourcing Equipmentdevice, said second subsystem couples to said first subsystem through asecond Ethernet cable and receives power to said second Powered Deviceand said second Power Sourcing Equipment device using Power overEthernet using the Power over Ethernet handshaking protocol, said secondpower switching device uses a transistor switch topology, said secondpower switching allows said second Power Sourcing Equipment to be turnedon without the need of stepping subsystem voltages, said second powerswitching device forwards the input power from said second PoweredDevice to said second Power Sourcing Equipment without disturbing thePoE handshaking between the devices; wherein from the output of saidfirst subsystem's first Power Sourcing Equipment device provides powerto the input of said second subsystem's second Power Sourcing Equipmentdevice.
 17. The system of claim 16 wherein said first subsystem and/orsaid second subsystem further comprises an intelligent switch coupled tothe power switching device.
 18. The system of claim 16 wherein saidfirst Power Sourcing Equipment device and/or said second Power SourcingEquipment device further comprises a battery.
 19. A non-transitoryprogram storage device readable by a computing device that tangiblyembodies a program of instructions executable by the computing device toperform a method to use a system for transmitting power to a remotePower over Ethernet (PoE) subsystem by forwarding Powered Device (PD)input voltage where the subsystem includes a Powered Device and a PowerSourcing Equipment device (PSE), comprising: providing a master PowerSourcing Equipment device; receiving power to a first subsystem, saidfirst subsystem further comprises a first Powered Device that includes afirst power switching device and a first Power Sourcing Equipmentdevice, said first subsystem couples to said master Power SourcingEquipment device through a first Ethernet cable and receives power tosaid first Powered Device and said first Power Sourcing Equipment deviceusing Power over Ethernet using the Power over Ethernet handshakingprotocol, said first power switching device uses an external switchingdevice that further includes a Zener diode coupled with a FETtransistor, said first power switching allows said first Power SourcingEquipment to be turned on without the need of stepping subsystemvoltages, said first power switching device forwards the input powerfrom said first Powered Device to said first Power Sourcing Equipmentwithout disturbing the PoE handshaking between the devices; andreceiving power to a second subsystem, said second subsystem furthercomprises a second Powered Device that includes a second power switchingdevice and a second Power Sourcing Equipment device, said secondsubsystem couples to said first subsystem through a second Ethernetcable and receives power to said second Powered Device and said secondPower Sourcing Equipment device using Power over Ethernet using thePower over Ethernet handshaking protocol, said second power switchingdevice uses an external switching device that further includes a Zenerdiode coupled with a FET transistor, said second power switching allowssaid second Power Sourcing Equipment to be turned on without the need ofstepping subsystem voltages, said second power switching device forwardsthe input power from said second Powered Device to said second PowerSourcing Equipment without disturbing the PoE handshaking between thedevices; wherein from the output of said first subsystem's first PowerSourcing Equipment device provides power to the input of said secondsubsystem's second Power Sourcing Equipment device.
 20. The device ofclaim 19 wherein said first subsystem and/or said second subsystemfurther comprises an intelligent switch coupled to the power switchingdevice.
 21. The device of claim 19 wherein said first Power SourcingEquipment device and/or said second Power Sourcing Equipment devicefurther comprises a battery.
 22. A non-transitory program storage devicereadable by a computing device that tangibly embodies a program ofinstructions executable by the computing device to perform a method touse a system for transmitting power to a remote Power over Ethernet(POE) subsystem by forwarding Powered Device (PD) input voltage wherethe subsystem includes a Powered Device and a Power Sourcing Equipmentdevice (PSE), comprising: providing a master Power Sourcing Equipmentdevice; receiving power to a first subsystem, said first subsystemfurther comprises a first Powered Device that includes a first powerswitching device and a first Power Sourcing Equipment device, said firstsubsystem couples to said master Power Sourcing Equipment device througha first Ethernet cable and receives power to said first Powered Deviceand said first Power Sourcing Equipment device using Power over Ethernetusing the Power over Ethernet handshaking protocol, said first powerswitching device uses an internal switching device that further includesa digital circuit using a MOSFET transistor, said first power switchingallows said first Power Sourcing Equipment to be turned on without theneed of stepping subsystem voltages, said first power switching deviceforwards the input power from said first Powered Device to said firstPower Sourcing Equipment without disturbing the PoE handshaking betweenthe devices; and receiving power to a second subsystem, said secondsubsystem further comprises a second Powered Device that includes asecond power switching device and a second Power Sourcing Equipmentdevice, said second subsystem couples to said first subsystem through asecond Ethernet cable and receives power to said second Powered Deviceand said second Power Sourcing Equipment device using Power overEthernet using the Power over Ethernet handshaking protocol, said secondpower switching device uses a transistor switch topology, said secondpower switching allows said second Power Sourcing Equipment to be turnedon without the need of stepping subsystem voltages, said second powerswitching device forwards the input power from said second PoweredDevice to said second Power Sourcing Equipment without disturbing thePoE handshaking between the devices; wherein from the output of saidfirst subsystem's first Power Sourcing Equipment device provides powerto the input of said second subsystem's second Power Sourcing Equipmentdevice.
 23. The system of claim 22 wherein said first subsystem and/orsaid second subsystem further comprises an intelligent switch coupled tothe power switching device.
 24. The system of claim 22 wherein saidfirst Power Sourcing Equipment device and/or said second Power SourcingEquipment device further comprises a battery.